Some web pages use a fixed font size, rather than setting it according to the browser preferences. On a low-resolutions screen (think: small laptop or TV), the fonts are big enough to be awkward. On a high-resolution screen (think: better-quality monitor) the fonts are so small as to be illegible. So use a font whose size is set by the user's browser.
Remember: the purpose of a web page always includes communication. Fixed-size fonts interfere with that.
Many times the fixed-size fonts are used to ensure that the web page has the same ``look'' as when the web page was prepared by the ``web design artist'' and approved by management. The artist and management should both try the web page on very low- and high-resolution screens!
Many people still use modems and other low-bandwidth links. Web page load times are often horrible because of the large graphics. Pick a few graphics of a few KB size and use them often instead of using lots of different graphics. Large graphics can often be small in KB if you are careful with the resolution and coloring.
Small computers often use wireless modems, so the communication speed is not getting better as fast as one might think. Large graphics take a long time to download because they are big. Many small graphics also take a long time to download because the HTTP protocol does not support ``get me this bunch of graphics.''
Review your web pages over a 28.8Kbaud modem before you approve them.
Many sites have W-I-D-E and T-A-L-L graphics with embedded navigation. On a small screen (think small laptop or TV), it is necessary to scroll just to see the whole graphic. This makes navigation hard and hurts usability of the web page.
Review your web page on a small screen before you approve it.
Frames work poorly on small screens (think small laptop or TV). Give yourself at most two frames in order to avoid using all of the screen real estate.
Review your web page on a small screen before you approve it.
Worry about barriers to accessibility.